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Ben Lindstrom9f049032002-06-21 00:59:05 +00001.\" -*- nroff -*-
2.\"
3.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5.\" All rights reserved
6.\"
7.\" As far as I am concerned, the code I have written for this software
8.\" can be used freely for any purpose. Any derived versions of this
9.\" software must be clearly marked as such, and if the derived work is
10.\" incompatible with the protocol description in the RFC file, it must be
11.\" called by a name other than "ssh" or "Secure Shell".
12.\"
13.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
14.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
15.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
16.\"
17.\" Redistribution and use in source and binary forms, with or without
18.\" modification, are permitted provided that the following conditions
19.\" are met:
20.\" 1. Redistributions of source code must retain the above copyright
21.\" notice, this list of conditions and the following disclaimer.
22.\" 2. Redistributions in binary form must reproduce the above copyright
23.\" notice, this list of conditions and the following disclaimer in the
24.\" documentation and/or other materials provided with the distribution.
25.\"
26.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36.\"
Damien Miller5a93add2003-01-24 11:34:52 +110037.\" $OpenBSD: sshd_config.5,v 1.14 2003/01/23 08:58:47 jmc Exp $
Ben Lindstrom9f049032002-06-21 00:59:05 +000038.Dd September 25, 1999
39.Dt SSHD_CONFIG 5
40.Os
41.Sh NAME
42.Nm sshd_config
43.Nd OpenSSH SSH daemon configuration file
44.Sh SYNOPSIS
45.Bl -tag -width Ds -compact
46.It Pa /etc/ssh/sshd_config
47.El
48.Sh DESCRIPTION
49.Nm sshd
50reads configuration data from
51.Pa /etc/ssh/sshd_config
52(or the file specified with
53.Fl f
54on the command line).
55The file contains keyword-argument pairs, one per line.
56Lines starting with
57.Ql #
58and empty lines are interpreted as comments.
59.Pp
60The possible
61keywords and their meanings are as follows (note that
62keywords are case-insensitive and arguments are case-sensitive):
63.Bl -tag -width Ds
64.It Cm AFSTokenPassing
65Specifies whether an AFS token may be forwarded to the server.
66Default is
67.Dq no .
68.It Cm AllowGroups
69This keyword can be followed by a list of group name patterns, separated
70by spaces.
71If specified, login is allowed only for users whose primary
72group or supplementary group list matches one of the patterns.
73.Ql \&*
74and
75.Ql ?
76can be used as
77wildcards in the patterns.
78Only group names are valid; a numerical group ID is not recognized.
79By default, login is allowed for all groups.
80.Pp
81.It Cm AllowTcpForwarding
82Specifies whether TCP forwarding is permitted.
83The default is
84.Dq yes .
85Note that disabling TCP forwarding does not improve security unless
86users are also denied shell access, as they can always install their
87own forwarders.
88.Pp
89.It Cm AllowUsers
90This keyword can be followed by a list of user name patterns, separated
91by spaces.
Damien Miller5a93add2003-01-24 11:34:52 +110092If specified, login is allowed only for user names that
Ben Lindstrom9f049032002-06-21 00:59:05 +000093match one of the patterns.
94.Ql \&*
95and
96.Ql ?
97can be used as
98wildcards in the patterns.
99Only user names are valid; a numerical user ID is not recognized.
100By default, login is allowed for all users.
101If the pattern takes the form USER@HOST then USER and HOST
102are separately checked, restricting logins to particular
103users from particular hosts.
104.Pp
105.It Cm AuthorizedKeysFile
106Specifies the file that contains the public keys that can be used
107for user authentication.
108.Cm AuthorizedKeysFile
109may contain tokens of the form %T which are substituted during connection
110set-up. The following tokens are defined: %% is replaced by a literal '%',
111%h is replaced by the home directory of the user being authenticated and
112%u is replaced by the username of that user.
113After expansion,
114.Cm AuthorizedKeysFile
115is taken to be an absolute path or one relative to the user's home
116directory.
117The default is
118.Dq .ssh/authorized_keys .
119.It Cm Banner
120In some jurisdictions, sending a warning message before authentication
121may be relevant for getting legal protection.
122The contents of the specified file are sent to the remote user before
123authentication is allowed.
124This option is only available for protocol version 2.
125By default, no banner is displayed.
126.Pp
127.It Cm ChallengeResponseAuthentication
128Specifies whether challenge response authentication is allowed.
129All authentication styles from
130.Xr login.conf 5
131are supported.
132The default is
133.Dq yes .
134.It Cm Ciphers
135Specifies the ciphers allowed for protocol version 2.
136Multiple ciphers must be comma-separated.
137The default is
138.Pp
139.Bd -literal
140 ``aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,
141 aes192-cbc,aes256-cbc''
142.Ed
143.It Cm ClientAliveInterval
144Sets a timeout interval in seconds after which if no data has been received
145from the client,
146.Nm sshd
147will send a message through the encrypted
148channel to request a response from the client.
149The default
150is 0, indicating that these messages will not be sent to the client.
151This option applies to protocol version 2 only.
152.It Cm ClientAliveCountMax
153Sets the number of client alive messages (see above) which may be
154sent without
155.Nm sshd
156receiving any messages back from the client. If this threshold is
157reached while client alive messages are being sent,
158.Nm sshd
159will disconnect the client, terminating the session. It is important
160to note that the use of client alive messages is very different from
161.Cm KeepAlive
162(below). The client alive messages are sent through the
163encrypted channel and therefore will not be spoofable. The TCP keepalive
164option enabled by
165.Cm KeepAlive
166is spoofable. The client alive mechanism is valuable when the client or
167server depend on knowing when a connection has become inactive.
168.Pp
169The default value is 3. If
170.Cm ClientAliveInterval
171(above) is set to 15, and
172.Cm ClientAliveCountMax
173is left at the default, unresponsive ssh clients
174will be disconnected after approximately 45 seconds.
175.It Cm Compression
176Specifies whether compression is allowed.
177The argument must be
178.Dq yes
179or
180.Dq no .
181The default is
182.Dq yes .
183.It Cm DenyGroups
184This keyword can be followed by a list of group name patterns, separated
185by spaces.
186Login is disallowed for users whose primary group or supplementary
187group list matches one of the patterns.
188.Ql \&*
189and
190.Ql ?
191can be used as
192wildcards in the patterns.
193Only group names are valid; a numerical group ID is not recognized.
194By default, login is allowed for all groups.
195.Pp
196.It Cm DenyUsers
197This keyword can be followed by a list of user name patterns, separated
198by spaces.
199Login is disallowed for user names that match one of the patterns.
200.Ql \&*
201and
202.Ql ?
203can be used as wildcards in the patterns.
204Only user names are valid; a numerical user ID is not recognized.
205By default, login is allowed for all users.
206If the pattern takes the form USER@HOST then USER and HOST
207are separately checked, restricting logins to particular
208users from particular hosts.
209.It Cm GatewayPorts
210Specifies whether remote hosts are allowed to connect to ports
211forwarded for the client.
212By default,
213.Nm sshd
214binds remote port forwardings to the loopback address. This
215prevents other remote hosts from connecting to forwarded ports.
216.Cm GatewayPorts
217can be used to specify that
218.Nm sshd
219should bind remote port forwardings to the wildcard address,
220thus allowing remote hosts to connect to forwarded ports.
221The argument must be
222.Dq yes
223or
224.Dq no .
225The default is
226.Dq no .
227.It Cm HostbasedAuthentication
228Specifies whether rhosts or /etc/hosts.equiv authentication together
229with successful public key client host authentication is allowed
230(hostbased authentication).
231This option is similar to
232.Cm RhostsRSAAuthentication
233and applies to protocol version 2 only.
234The default is
235.Dq no .
236.It Cm HostKey
237Specifies a file containing a private host key
238used by SSH.
239The default is
240.Pa /etc/ssh/ssh_host_key
241for protocol version 1, and
242.Pa /etc/ssh/ssh_host_rsa_key
243and
244.Pa /etc/ssh/ssh_host_dsa_key
245for protocol version 2.
246Note that
247.Nm sshd
248will refuse to use a file if it is group/world-accessible.
249It is possible to have multiple host key files.
250.Dq rsa1
251keys are used for version 1 and
252.Dq dsa
253or
254.Dq rsa
255are used for version 2 of the SSH protocol.
256.It Cm IgnoreRhosts
257Specifies that
258.Pa .rhosts
259and
260.Pa .shosts
261files will not be used in
262.Cm RhostsAuthentication ,
263.Cm RhostsRSAAuthentication
264or
265.Cm HostbasedAuthentication .
266.Pp
267.Pa /etc/hosts.equiv
268and
269.Pa /etc/shosts.equiv
270are still used.
271The default is
272.Dq yes .
273.It Cm IgnoreUserKnownHosts
274Specifies whether
275.Nm sshd
276should ignore the user's
277.Pa $HOME/.ssh/known_hosts
278during
279.Cm RhostsRSAAuthentication
280or
281.Cm HostbasedAuthentication .
282The default is
283.Dq no .
284.It Cm KeepAlive
285Specifies whether the system should send TCP keepalive messages to the
286other side.
287If they are sent, death of the connection or crash of one
288of the machines will be properly noticed.
289However, this means that
290connections will die if the route is down temporarily, and some people
291find it annoying.
292On the other hand, if keepalives are not sent,
293sessions may hang indefinitely on the server, leaving
294.Dq ghost
295users and consuming server resources.
296.Pp
297The default is
298.Dq yes
299(to send keepalives), and the server will notice
300if the network goes down or the client host crashes.
301This avoids infinitely hanging sessions.
302.Pp
303To disable keepalives, the value should be set to
304.Dq no .
305.It Cm KerberosAuthentication
306Specifies whether Kerberos authentication is allowed.
307This can be in the form of a Kerberos ticket, or if
Ben Lindstrom9f049032002-06-21 00:59:05 +0000308.Cm PasswordAuthentication
309is yes, the password provided by the user will be validated through
310the Kerberos KDC.
311To use this option, the server needs a
312Kerberos servtab which allows the verification of the KDC's identity.
313Default is
314.Dq no .
315.It Cm KerberosOrLocalPasswd
316If set then if password authentication through Kerberos fails then
317the password will be validated via any additional local mechanism
318such as
319.Pa /etc/passwd .
320Default is
321.Dq yes .
322.It Cm KerberosTgtPassing
323Specifies whether a Kerberos TGT may be forwarded to the server.
324Default is
325.Dq no ,
326as this only works when the Kerberos KDC is actually an AFS kaserver.
327.It Cm KerberosTicketCleanup
328Specifies whether to automatically destroy the user's ticket cache
329file on logout.
330Default is
331.Dq yes .
332.It Cm KeyRegenerationInterval
333In protocol version 1, the ephemeral server key is automatically regenerated
334after this many seconds (if it has been used).
335The purpose of regeneration is to prevent
336decrypting captured sessions by later breaking into the machine and
337stealing the keys.
338The key is never stored anywhere.
339If the value is 0, the key is never regenerated.
340The default is 3600 (seconds).
341.It Cm ListenAddress
342Specifies the local addresses
343.Nm sshd
344should listen on.
345The following forms may be used:
346.Pp
347.Bl -item -offset indent -compact
348.It
349.Cm ListenAddress
350.Sm off
351.Ar host No | Ar IPv4_addr No | Ar IPv6_addr
352.Sm on
353.It
354.Cm ListenAddress
355.Sm off
356.Ar host No | Ar IPv4_addr No : Ar port
357.Sm on
358.It
359.Cm ListenAddress
360.Sm off
361.Oo
362.Ar host No | Ar IPv6_addr Oc : Ar port
363.Sm on
364.El
365.Pp
366If
367.Ar port
368is not specified,
369.Nm sshd
370will listen on the address and all prior
371.Cm Port
372options specified. The default is to listen on all local
373addresses. Multiple
374.Cm ListenAddress
375options are permitted. Additionally, any
376.Cm Port
377options must precede this option for non port qualified addresses.
378.It Cm LoginGraceTime
379The server disconnects after this time if the user has not
380successfully logged in.
381If the value is 0, there is no time limit.
Damien Millerc1348632002-09-05 14:35:14 +1000382The default is 120 seconds.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000383.It Cm LogLevel
384Gives the verbosity level that is used when logging messages from
385.Nm sshd .
386The possible values are:
387QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2 and DEBUG3.
388The default is INFO. DEBUG and DEBUG1 are equivalent. DEBUG2
389and DEBUG3 each specify higher levels of debugging output.
390Logging with a DEBUG level violates the privacy of users
391and is not recommended.
392.It Cm MACs
393Specifies the available MAC (message authentication code) algorithms.
394The MAC algorithm is used in protocol version 2
395for data integrity protection.
396Multiple algorithms must be comma-separated.
397The default is
398.Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 .
399.It Cm MaxStartups
400Specifies the maximum number of concurrent unauthenticated connections to the
401.Nm sshd
402daemon.
403Additional connections will be dropped until authentication succeeds or the
404.Cm LoginGraceTime
405expires for a connection.
406The default is 10.
407.Pp
408Alternatively, random early drop can be enabled by specifying
409the three colon separated values
410.Dq start:rate:full
411(e.g., "10:30:60").
412.Nm sshd
413will refuse connection attempts with a probability of
414.Dq rate/100
415(30%)
416if there are currently
417.Dq start
418(10)
419unauthenticated connections.
420The probability increases linearly and all connection attempts
421are refused if the number of unauthenticated connections reaches
422.Dq full
423(60).
Damien Miller136d4412002-06-26 23:05:16 +1000424.It Cm PAMAuthenticationViaKbdInt
425Specifies whether PAM challenge response authentication is allowed. This
426allows the use of most PAM challenge response authentication modules, but
427it will allow password authentication regardless of whether
428.Cm PasswordAuthentication
429is enabled.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000430.It Cm PasswordAuthentication
431Specifies whether password authentication is allowed.
432The default is
433.Dq yes .
434.It Cm PermitEmptyPasswords
435When password authentication is allowed, it specifies whether the
436server allows login to accounts with empty password strings.
437The default is
438.Dq no .
439.It Cm PermitRootLogin
440Specifies whether root can login using
441.Xr ssh 1 .
442The argument must be
443.Dq yes ,
444.Dq without-password ,
445.Dq forced-commands-only
446or
447.Dq no .
448The default is
449.Dq yes .
450.Pp
451If this option is set to
452.Dq without-password
453password authentication is disabled for root.
454.Pp
455If this option is set to
456.Dq forced-commands-only
457root login with public key authentication will be allowed,
458but only if the
459.Ar command
460option has been specified
461(which may be useful for taking remote backups even if root login is
462normally not allowed). All other authentication methods are disabled
463for root.
464.Pp
465If this option is set to
466.Dq no
467root is not allowed to login.
Ben Lindstrom5d860f02002-08-01 01:28:38 +0000468.It Cm PermitUserEnvironment
469Specifies whether
470.Pa ~/.ssh/environment
Ben Lindstrombd9bf382002-08-20 18:54:20 +0000471and
Ben Lindstrom5d860f02002-08-01 01:28:38 +0000472.Cm environment=
473options in
474.Pa ~/.ssh/authorized_keys
Ben Lindstrombd9bf382002-08-20 18:54:20 +0000475are processed by
476.Nm sshd .
Ben Lindstrom5d860f02002-08-01 01:28:38 +0000477The default is
478.Dq no .
Ben Lindstrombd9bf382002-08-20 18:54:20 +0000479Enabling environment processing may enable users to bypass access
480restrictions in some configurations using mechanisms such as
481.Ev LD_PRELOAD .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000482.It Cm PidFile
Ben Lindstrom959de992002-06-23 00:35:25 +0000483Specifies the file that contains the process ID of the
Ben Lindstrom9f049032002-06-21 00:59:05 +0000484.Nm sshd
485daemon.
486The default is
487.Pa /var/run/sshd.pid .
488.It Cm Port
489Specifies the port number that
490.Nm sshd
491listens on.
492The default is 22.
493Multiple options of this type are permitted.
494See also
495.Cm ListenAddress .
496.It Cm PrintLastLog
497Specifies whether
498.Nm sshd
499should print the date and time when the user last logged in.
500The default is
501.Dq yes .
502.It Cm PrintMotd
503Specifies whether
504.Nm sshd
505should print
506.Pa /etc/motd
507when a user logs in interactively.
508(On some systems it is also printed by the shell,
509.Pa /etc/profile ,
510or equivalent.)
511The default is
512.Dq yes .
513.It Cm Protocol
514Specifies the protocol versions
515.Nm sshd
Ben Lindstrom9c445542002-07-11 03:59:18 +0000516supports.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000517The possible values are
518.Dq 1
519and
520.Dq 2 .
521Multiple versions must be comma-separated.
522The default is
523.Dq 2,1 .
Ben Lindstrom9c445542002-07-11 03:59:18 +0000524Note that the order of the protocol list does not indicate preference,
525because the client selects among multiple protocol versions offered
526by the server.
527Specifying
528.Dq 2,1
529is identical to
530.Dq 1,2 .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000531.It Cm PubkeyAuthentication
532Specifies whether public key authentication is allowed.
533The default is
534.Dq yes .
535Note that this option applies to protocol version 2 only.
536.It Cm RhostsAuthentication
537Specifies whether authentication using rhosts or /etc/hosts.equiv
538files is sufficient.
539Normally, this method should not be permitted because it is insecure.
540.Cm RhostsRSAAuthentication
541should be used
542instead, because it performs RSA-based host authentication in addition
543to normal rhosts or /etc/hosts.equiv authentication.
544The default is
545.Dq no .
546This option applies to protocol version 1 only.
547.It Cm RhostsRSAAuthentication
548Specifies whether rhosts or /etc/hosts.equiv authentication together
549with successful RSA host authentication is allowed.
550The default is
551.Dq no .
552This option applies to protocol version 1 only.
553.It Cm RSAAuthentication
554Specifies whether pure RSA authentication is allowed.
555The default is
556.Dq yes .
557This option applies to protocol version 1 only.
558.It Cm ServerKeyBits
559Defines the number of bits in the ephemeral protocol version 1 server key.
560The minimum value is 512, and the default is 768.
561.It Cm StrictModes
562Specifies whether
563.Nm sshd
564should check file modes and ownership of the
565user's files and home directory before accepting login.
566This is normally desirable because novices sometimes accidentally leave their
567directory or files world-writable.
568The default is
569.Dq yes .
570.It Cm Subsystem
571Configures an external subsystem (e.g., file transfer daemon).
572Arguments should be a subsystem name and a command to execute upon subsystem
573request.
574The command
575.Xr sftp-server 8
576implements the
577.Dq sftp
578file transfer subsystem.
579By default no subsystems are defined.
580Note that this option applies to protocol version 2 only.
581.It Cm SyslogFacility
582Gives the facility code that is used when logging messages from
583.Nm sshd .
584The possible values are: DAEMON, USER, AUTH, LOCAL0, LOCAL1, LOCAL2,
585LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7.
586The default is AUTH.
587.It Cm UseLogin
588Specifies whether
589.Xr login 1
590is used for interactive login sessions.
591The default is
592.Dq no .
593Note that
594.Xr login 1
595is never used for remote command execution.
596Note also, that if this is enabled,
597.Cm X11Forwarding
598will be disabled because
599.Xr login 1
600does not know how to handle
601.Xr xauth 1
602cookies. If
603.Cm UsePrivilegeSeparation
604is specified, it will be disabled after authentication.
605.It Cm UsePrivilegeSeparation
606Specifies whether
607.Nm sshd
608separates privileges by creating an unprivileged child process
609to deal with incoming network traffic. After successful authentication,
610another process will be created that has the privilege of the authenticated
611user. The goal of privilege separation is to prevent privilege
612escalation by containing any corruption within the unprivileged processes.
613The default is
614.Dq yes .
615.It Cm VerifyReverseMapping
616Specifies whether
617.Nm sshd
618should try to verify the remote host name and check that
619the resolved host name for the remote IP address maps back to the
620very same IP address.
621The default is
622.Dq no .
623.It Cm X11DisplayOffset
624Specifies the first display number available for
625.Nm sshd Ns 's
626X11 forwarding.
627This prevents
628.Nm sshd
629from interfering with real X11 servers.
630The default is 10.
631.It Cm X11Forwarding
632Specifies whether X11 forwarding is permitted.
Damien Miller101c4a72002-09-19 11:51:21 +1000633The argument must be
634.Dq yes
635or
636.Dq no .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000637The default is
638.Dq no .
Damien Miller101c4a72002-09-19 11:51:21 +1000639.Pp
640When X11 forwarding is enabled, there may be additional exposure to
641the server and to client displays if the
642.Nm sshd
643proxy display is configured to listen on the wildcard address (see
644.Cm X11UseLocalhost
645below), however this is not the default.
646Additionally, the authentication spoofing and authentication data
647verification and substitution occur on the client side.
648The security risk of using X11 forwarding is that the client's X11
649display server may be exposed to attack when the ssh client requests
650forwarding (see the warnings for
651.Cm ForwardX11
652in
653.Xr ssh_config 5 ).
654A system administrator may have a stance in which they want to
655protect clients that may expose themselves to attack by unwittingly
656requesting X11 forwarding, which can warrant a
657.Dq no
658setting.
659.Pp
660Note that disabling X11 forwarding does not prevent users from
661forwarding X11 traffic, as users can always install their own forwarders.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000662X11 forwarding is automatically disabled if
663.Cm UseLogin
664is enabled.
665.It Cm X11UseLocalhost
666Specifies whether
667.Nm sshd
668should bind the X11 forwarding server to the loopback address or to
669the wildcard address. By default,
670.Nm sshd
671binds the forwarding server to the loopback address and sets the
672hostname part of the
673.Ev DISPLAY
674environment variable to
675.Dq localhost .
Ben Lindstrom15b61202002-08-20 18:44:24 +0000676This prevents remote hosts from connecting to the proxy display.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000677However, some older X11 clients may not function with this
678configuration.
679.Cm X11UseLocalhost
680may be set to
681.Dq no
682to specify that the forwarding server should be bound to the wildcard
683address.
684The argument must be
685.Dq yes
686or
687.Dq no .
688The default is
689.Dq yes .
690.It Cm XAuthLocation
Damien Miller05913ba2002-09-04 16:51:03 +1000691Specifies the full pathname of the
Ben Lindstrom9f049032002-06-21 00:59:05 +0000692.Xr xauth 1
693program.
694The default is
695.Pa /usr/X11R6/bin/xauth .
696.El
697.Ss Time Formats
698.Pp
699.Nm sshd
700command-line arguments and configuration file options that specify time
701may be expressed using a sequence of the form:
702.Sm off
Ben Lindstrom1f8cf4f2002-08-20 18:43:27 +0000703.Ar time Op Ar qualifier ,
Ben Lindstrom9f049032002-06-21 00:59:05 +0000704.Sm on
705where
706.Ar time
707is a positive integer value and
708.Ar qualifier
709is one of the following:
710.Pp
711.Bl -tag -width Ds -compact -offset indent
712.It Cm <none>
713seconds
714.It Cm s | Cm S
715seconds
716.It Cm m | Cm M
717minutes
718.It Cm h | Cm H
719hours
720.It Cm d | Cm D
721days
722.It Cm w | Cm W
723weeks
724.El
725.Pp
726Each member of the sequence is added together to calculate
727the total time value.
728.Pp
729Time format examples:
730.Pp
731.Bl -tag -width Ds -compact -offset indent
732.It 600
733600 seconds (10 minutes)
734.It 10m
73510 minutes
736.It 1h30m
7371 hour 30 minutes (90 minutes)
738.El
739.Sh FILES
740.Bl -tag -width Ds
741.It Pa /etc/ssh/sshd_config
742Contains configuration data for
743.Nm sshd .
744This file should be writable by root only, but it is recommended
745(though not necessary) that it be world-readable.
746.El
747.Sh AUTHORS
748OpenSSH is a derivative of the original and free
749ssh 1.2.12 release by Tatu Ylonen.
750Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
751Theo de Raadt and Dug Song
752removed many bugs, re-added newer features and
753created OpenSSH.
754Markus Friedl contributed the support for SSH
755protocol versions 1.5 and 2.0.
756Niels Provos and Markus Friedl contributed support
757for privilege separation.
758.Sh SEE ALSO
759.Xr sshd 8